The spatial relation between young star clusters and molecular clouds in M51 with LEGUS
Date
2019
Authors
Grasha, Kathryn
Calzetti, Daniela
Adamo, A.
Kennicutt, Robert C
Elmegreen, B. G.
Messa, M
Dale, Daniel A
Fedorenko, K
Mahadevan, S
Grebel, E.
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Royal Astronomical Society
Abstract
We present a study correlating the spatial locations of young star clusters with those of
molecular clouds in NGC 5194, in order to investigate the time-scale over which clusters
separate from their birth clouds. The star cluster catalogues are from the Legacy ExtraGalactic
UV Survey (LEGUS) and the molecular clouds from the Plateau de Bure Interefrometer
Arcsecond Whirpool Survey (PAWS). We find that younger star clusters are spatially closer to
molecular clouds than older star clusters. The median age for clusters associated with clouds
is 4 Myr, whereas it is 50 Myr for clusters that are sufficiently separated from a molecular
cloud to be considered unassociated. After ∼6 Myr, the majority of the star clusters lose
association with their molecular gas. Younger star clusters are also preferentially located
in stellar spiral arms where they are hierarchically distributed in kpc-size regions for 50–
100 Myr before dispersing. The youngest star clusters are more strongly clustered, yielding
a two-point correlation function with α = −0.28 ± 0.04, than the giant molecular cloud
(GMCs) (α = −0.09 ± 0.03) within the same PAWS field. However, the clustering strength of
the most massive GMCs, supposedly the progenitors of the young clusters for a star formation
efficiency of a few per cent, is comparable (α = −0.35 ± 0.05) to that of the clusters.
We find a galactocentric dependence for the coherence of star formation, in which clusters
located in the inner region of the galaxy reside in smaller star-forming complexes and display
more homogeneous distributions than clusters further from the centre. This result suggests a
correlation between the survival of a cluster complex and its environment.
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Keywords
ISM: clouds, galaxies: individual (NGC 5194, M 51), galaxies: star clusters: general, galaxies: star formation, galaxies: stellar content, galaxies: structure
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Monthly Notices of the Royal Astronomical Society
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Journal article
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Open Access
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